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// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_COMPILER_LOOP_UNROLLING_H_
#define V8_COMPILER_LOOP_UNROLLING_H_
// Loop unrolling is an optimization that copies the body of a loop and creates
// a fresh loop, whose iteration corresponds to 2 or more iterations of the
// initial loop. For a high-level description of the algorithm see
// docs.google.com/document/d/1AsUCqslMUB6fLdnGq0ZoPk2kn50jIJAWAL77lKXXP5g/
#include "src/compiler/common-operator.h"
#include "src/compiler/loop-analysis.h"
namespace v8 {
namespace internal {
namespace compiler {
static constexpr uint32_t kMaximumUnnestedSize = 50;
static constexpr uint32_t kMaximumUnrollingCount = 7;
// A simple heuristic to decide how many times to unroll a loop. Favors small
// and deeply nested loops.
// TODO(manoskouk): Investigate how this can be improved.
V8_INLINE uint32_t unrolling_count_heuristic(uint32_t size, uint32_t depth) {
return std::min((depth + 1) * kMaximumUnnestedSize / size,
kMaximumUnrollingCount);
}
V8_INLINE uint32_t maximum_unrollable_size(uint32_t depth) {
return (depth + 1) * kMaximumUnnestedSize;
}
void UnrollLoop(Node* loop_node, ZoneUnorderedSet<Node*>* loop, uint32_t depth,
Graph* graph, CommonOperatorBuilder* common, Zone* tmp_zone,
SourcePositionTable* source_positions,
NodeOriginTable* node_origins);
} // namespace compiler
} // namespace internal
} // namespace v8
#endif // V8_COMPILER_LOOP_UNROLLING_H_
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